MariaDB 10.1 Galera CentOS 7

CentOS 7 MariaDB 10.1 Galera cluster installation from the official MariaDB repository. Uses xtrabackup for state transfer. Image wil automatically run any sql scripts present in /docker-entrypoint-initdb.d as part of startup.

Required Variables

CLUSTER=Can be either BOOTSTRAP, STANDALONE or a comma-separated list of container names

Once the initial cluster instance is bootstrapped, you can start the remaining cluster members by specifying the list of possible nodes in the run command. Below assumes you're running all three nodes on the same system for testing purposes:

What is MariaDB?

MariaDB is a community-developed fork of the MySQL relational database management system intended to remain free under the GNU GPL. Being a fork of a leading open source software system, it is notable for being led by the original developers of MySQL, who forked it due to concerns over its acquisition by Oracle. Contributors are required to share their copyright with the MariaDB Foundation.

The intent is also to maintain high compatibility with MySQL, ensuring a "drop-in" replacement capability with library binary equivalency and exact matching with MySQL APIs and commands. It includes the XtraDB storage engine for replacing InnoDB, as well as a new storage engine, Aria, that intends to be both a transactional and non-transactional engine perhaps even included in future versions of MySQL.

How to use this image

Start a mariadb server instance

... where some-mariadb is the name you want to assign to your container, my-secret-pw is the password to be set for the MySQL root user and tag is the tag specifying the MySQL version you want. See the list above for relevant tags.

Connect to MySQL from an application in another Docker container

Since MariaDB is intended as a drop-in replacement for MySQL, it can be used with many applications. This image exposes the standard MySQL port (3306), so container linking makes the MySQL instance available to other application containers. Start your application container like this in order to link it to the MySQL container:

Connect to MariaDB from the MySQL command line client

The following command starts another mariadb container instance and runs the mysql command line client against your original mariadb container, allowing you to execute SQL statements against your database instance:

Container shell access and viewing MySQL logs

The docker exec command allows you to run commands inside a Docker container. The following command line will give you a bash shell inside your mariadb container:

$ docker exec -it some-mariadb bash

The MariaDB Server log is available through Docker's container log:

$ docker logs some-mariadb

Using a custom MySQL configuration file

The MariaDB startup configuration is specified in the file /etc/mysql/my.cnf, and that file in turn includes any files found in the /etc/mysql/conf.d directory that end with .cnf. Settings in files in this directory will augment and/or override settings in /etc/mysql/my.cnf. If you want to use a customized MySQL configuration, you can create your alternative configuration file in a directory on the host machine and then mount that directory location as /etc/mysql/conf.d inside the mariadb container.

If /my/custom/config-file.cnf is the path and name of your custom configuration file, you can start your mariadb container like this (note that only the directory path of the custom config file is used in this command):

This will start a new container some-mariadb where the MariaDB instance uses the combined startup settings from /etc/mysql/my.cnf and /etc/mysql/conf.d/config-file.cnf, with settings from the latter taking precedence.

Note that users on host systems with SELinux enabled may see issues with this. The current workaround is to assign the relevant SELinux policy type to your new config file so that the container will be allowed to mount it:

$ chcon -Rt svirt_sandbox_file_t /my/custom

Environment Variables

When you start the mariadb image, you can adjust the configuration of the MariaDB instance by passing one or more environment variables on the docker run command line. Do note that none of the variables below will have any effect if you start the container with a data directory that already contains a database: any pre-existing database will always be left untouched on container startup.

MYSQL_ROOT_PASSWORD

This variable is mandatory and specifies the password that will be set for the MariaDB root superuser account. In the above example, it was set to my-secret-pw.

MYSQL_DATABASE

This variable is optional and allows you to specify the name of a database to be created on image startup. If a user/password was supplied (see below) then that user will be granted superuser access (corresponding to GRANT ALL) to this database.

MYSQL_USER, MYSQL_PASSWORD

These variables are optional, used in conjunction to create a new user and to set that user's password. This user will be granted superuser permissions (see above) for the database specified by the MYSQL_DATABASE variable. Both variables are required for a user to be created.

Do note that there is no need to use this mechanism to create the root superuser, that user gets created by default with the password specified by the MYSQL_ROOT_PASSWORD variable.

MYSQL_ALLOW_EMPTY_PASSWORD

This is an optional variable. Set to yes to allow the container to be started with a blank password for the root user. NOTE: Setting this variable to yes is not recommended unless you really know what you are doing, since this will leave your MariaDB instance completely unprotected, allowing anyone to gain complete superuser access.

Initializing a fresh instance

When a container is started for the first time, a new database mysql will be initialized with the provided configuration variables. Furthermore, it will execute files with extensions .sh and .sql that are found in /docker-entrypoint-initdb.d. You can easily populate your mariadb services by mounting a SQL dump into that directory and provide custom images with contributed data.

Caveats

Where to Store Data

Important note: There are several ways to store data used by applications that run in Docker containers. We encourage users of the mariadb images to familiarize themselves with the options available, including:

Create a data directory on the host system (outside the container) and mount this to a directory visible from inside the container. This places the database files in a known location on the host system, and makes it easy for tools and applications on the host system to access the files. The downside is that the user needs to make sure that the directory exists, and that e.g. directory permissions and other security mechanisms on the host system are set up correctly.

The Docker documentation is a good starting point for understanding the different storage options and variations, and there are multiple blogs and forum postings that discuss and give advice in this area. We will simply show the basic procedure here for the latter option above:

The -v /my/own/datadir:/var/lib/mysql part of the command mounts the /my/own/datadir directory from the underlying host system as /var/lib/mysql inside the container, where MySQL by default will write its data files.

Note that users on host systems with SELinux enabled may see issues with this. The current workaround is to assign the relevant SELinux policy type to the new data directory so that the container will be allowed to access it:

$ chcon -Rt svirt_sandbox_file_t /my/own/datadir

No connections until MySQL init completes

If there is no database initialized when the container starts, then a default database will be created. While this is the expected behavior, this means that it will not accept incoming connections until such initialization completes. This may cause issues when using automation tools, such as docker-compose, which start several containers simultaneously.

Usage against an existing database

If you start your mariadb container instance with a data directory that already contains a database (specifically, a mysql subdirectory), the $MYSQL_ROOT_PASSWORD variable should be omitted from the run command line; it will in any case be ignored, and the pre-existing database will not be changed in any way.

Supported Docker versions

This image is officially supported on Docker version 1.9.1.

Support for older versions (down to 1.6) is provided on a best-effort basis.

Issues

If you have any problems with or questions about this image, please contact us through a GitHub issue.

You can also reach many of the official image maintainers via the #docker-library IRC channel on Freenode.

Contributing

You are invited to contribute new features, fixes, or updates, large or small; we are always thrilled to receive pull requests, and do our best to process them as fast as we can.

Before you start to code, we recommend discussing your plans through a GitHub issue, especially for more ambitious contributions. This gives other contributors a chance to point you in the right direction, give you feedback on your design, and help you find out if someone else is working on the same thing.